Arterial Blood Gas Analysis (ABG)

Purpose of the test:
*Evaluates gas exchange in the lungs (Measurements may be needed to make diagnosis or to monitor various treatments)

Risks and precautions:
Some blood may leak from the artery after blood has been withdrawn. This is usually controlled easily. If you are treated with intermittent positive-pressure breathing, the operator should wait at least 20 minutes after treatment to draw arterial blood.

Patient preparation:
None required if blood is collected from an artery in the arm. Partial disrobing is necessary if a technician, nurse or doctor chooses the artery in the groin or under the armpit.

Description of test:
Operator feels the artery to be punctured. Skin over the artery is cleaned with alcohol or other antiseptic on a piece of cotton.
The site is draped
Skin is injected with a local anesthetic, such as Xylocaine
The artery is punctured with a sterile, disposable needle attached to a disposable syringe. Operator withdraws the needle and transfers sample from the collecting syringe into sterile tubes.
You will feel some minor pain when the local anesthetic is injected into the skin overlying the artery before collecting blood. You may feel slight additional discomfort when the underlying artery is punctured.
Tubes are packed in an ice bag before transporting to the laboratory.

Activity after test:
Rest quietly for 10 minutes, applying pressure to arterial puncture site; Use warm compresses if blood collects under the puncture site or if the area becomes tender, red or painful

Time before test results available:
1 to 2 hours if done in hospital or local lab. Several days if a distant lab analyzes samples.

Time before test results available:
Test requires only a few minutes in the laboratory. Time before results are reported to the doctor varies from a few minutes to a few days.

Normal Values:
Adult indirect bilirubin levels--1.1 mg/dl or less
Adult direct bilirubin levels--Less than 0.5 mg/dl
Total bilirubin in a newborn--1 to 12mg/dl

What "high" or "increased" may indicate:
Congenital enzyme deficiencies (Gilbert's disease)
Liver damage
Severe hemolytic anemia
Obstruction of bile ducts from stones or tumors
If over 20mg/dl in a newborn, exchange transfusion may be needed